1 /* 2 * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "utilities/globalDefinitions.hpp" 26 27 class Unsafe { 28 public: 29 // Note: The VM's obj_field and related accessors use byte-scaled 30 // ("unscaled") offsets, just as the unsafe methods do. 31 32 // However, the method Unsafe.fieldOffset explicitly declines to 33 // guarantee this. The field offset values manipulated by the Java user 34 // through the Unsafe API are opaque cookies that just happen to be byte 35 // offsets. We represent this state of affairs by passing the cookies 36 // through conversion functions when going between the VM and the Unsafe API. 37 // The conversion functions just happen to be no-ops at present. 38 enum { 39 final_bits = 1, 40 offset_bits = BitsPerLong - final_bits, 41 42 final_shift = 0, 43 offset_shift = final_bits, 44 45 final_mask = right_n_bits(final_bits) 46 }; 47 48 static jlong field_offset_to_byte_offset(jlong field_offset) { 49 return (field_offset >> offset_shift); 50 } 51 52 static jlong field_offset_from_byte_offset(jlong byte_offset, bool is_final = false) { 53 return (byte_offset << offset_shift) | (is_final ? final_mask : 0); 54 } 55 56 static jint invocation_key_from_method_slot(jint slot) { 57 return slot; 58 } 59 60 static jint invocation_key_to_method_slot(jint key) { 61 return key; 62 } 63 }; 64